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Definition of a vector and a vector-borne disease
|Author(s) :||D.W. Verwoerd|
A vector can be defined, in a biomedical context, as a living being (most usually an arthropod) capable of transmitting a disease to vertebrate hosts, including humans. A basic distinction can be made between mechanical vectors and biological vectors. Mechanical vectors, in any of the classes of haematophagous arthropods, are infected during a blood meal with a microorganism which is transmitted to a second host without any multiplication cycle in the vector. The infection of the vector is usually of short duration in such cases. A discussion of the complex variables involved in mechanical transmission can be found in the second issue of this volume of the Scientific and Technical Review of the World Organisation for Animal Health (the Review) (1). In contrast, in the case of a biological vector the infectious organism undergoes a cycle of multiplication in the vector, which remains infective and may transmit the infection to its progeny. From an epidemiological point of view the latter class of vector is much more important than the former in terms of its ability to start and maintain a disease outbreak.